Video Conferencing Problem

Does anyone know why I cannot hold a video conference
through MSN/Netmeeting with a computer that does not run
XP.

I run XP and can successfully conference with people also
running XP through Windows Messenger. But not everyone
has XP operating system!

All my problems have arisen since upgrading to XP as I
was able to conference with anyone sucessfully before
that. I cannot believe that Microsoft have made video
conferencing impossible if you are not running XP. Do
they not have enough of the market already???

So, if anyone can solve my problem or suggest anything to
allow me to video conference (apart from upgrading to
XP!) I would be grateful!!!

you need to make sure these ports are open in the windows firewall

Port Purpose
-------------------------------------
389 Internet Locator Server [Transmission Control Protocol (TCP)]
522 User Location Server (TCP)
1503 T.120 (TCP)
1720 H.323 call setup (TCP)
1731 Audio call control (TCP)
Dynamic H.323 call control (TCP)
Dynamic H.323 streaming [Realtime Transport Protocol (RTP) over User Datagram Protocol (UDP)]